The invention relates generally to belt conveyors and, more particularly, to a passive article-transfer assembly for stripping articles from an off-loading end of a conveyor belt.
Endless conveyor belts are used widely to transport products, or articles. In many applications, the articles must be transferred from the conveying surface of a moving belt to another belt or to a stationary work station. Article transfer assemblies, such as finger transfer plates and dead plates closely abutting the belt as it passes around rotating sprockets or drums at an off-loading end of a conveyor belt, provide for a smooth continuation of product flow from the belt as it engages its sprockets or drums to begin its return trip.
A finger transfer plate includes a comb-like structure with teeth, or fingers, extending from a receiving platform into channels formed between longitudinal ridges defining the top conveying surface of a raised-rib conveyor belt. The transfer plate is disposed roughly tangent to the belt as it passes around its sprocket. By meshing with the ridges on the belt, the fingers strip articles from the conveying surface of the moving belt. The tops of the fingers and the receiving platform form a continuation of the conveying surface of the belt. Articles stripped from the moving belt push leading articles along the top surface of the finger plate for transfer to another belt or to a work station.
Dead plates perform a similar function. Lacking the fingers of a finger plate and the ability to mesh with the ridges of a raised-rib belt, a dead plate usually has a beveled edge that closely abuts, across a small gap, a belt passing over a sprocket. The top surface of the dead plate forms an extension of the belt's conveying surface for the transfer of conveyed articles off a conveyor belt.
One problem with dead plates and finger plates is the friction between the stationary flat surface of the plates and the articles pushing each other along that surface. The friction impedes the flow of the articles. Besides active means of urging products along the plates, various passive solutions have been tried. For example, extending the fingers of a finger transfer plate farther back into the platform area can decrease the friction. As another example, sets of rollers have been installed to replace the flat platform surface with a rolling surface. One of the shortcomings of these solutions is their susceptibility to damage or degraded performance in certain applications, such as in glass-handling, where pieces of glass can become wedged between the finger extensions or between the rollers. The wedged glass can cause the fingers or the ridges of a raised-rib conveyor belt to chip or break off or can cause the fingers to deflect and bind against the ridges, jamming the belt. Furthermore, extended fingers and rollers are also more difficult to clean, an important consideration in food-handling industries.
The long, slender fingers of finger plates are especially susceptible to breaking. Once enough fingers are broken, the entire finger plate must be discarded and replaced. For that reason, finger plates are often made of fairly strong and resilient materials. Unfortunately, the friction characteristics of such materials arc not favorable. There is a tradeoff between high durability for long-lasting fingers and low friction for easy article transfer along the finger plate receiving platform.
Consequently, there is a need for an article transfer assembly that combines a durable, belt-abutting, product-stripping section with a low-friction receiving platform to facilitate the flow of product off a moving conveyor belt.